Membrane Transporters in Drug Development Dr Raymond Evers Merck - PowerPoint PPT Presentation

Membrane Transporters in Drug Development Dr Raymond Evers Merck & Co Drug Metabolism and Pharmacokinetics P.O. Box 2000 Rahway, NJ 08816 Raymond_Evers@merck.com

Outline  Part 1  Overview of the ITC  Transporters covered by the ITC  Decision trees  Part 2  Case Studies  OATP-mediated DDIs  Digoxin-Rifampin DDI 2

Transporters and the FDA (Critical Path Initiative) 3

Goals of the International Transporter Consortium Provide an update on the current thinking on transporters  For in vitro studies, provide a focus on studies that can have a  translational clinical interpretation Limit raising red flags with in vitro studies that cannot be addressed  in vivo in the clinic Explore gaps and suggest ways forward  Provide a coordinated approach: academia, industry and regulatory  Help to move the science forward  Decision trees to assist drug development and regulatory agencies  Consensus on current scientific status  Gather support to move the ADME transport area forward  4

International Transporter Consortium Workshop Bethesda North Marriott October 2 nd and 3 rd , 2008 • Sponsored by FDA Critical Path • Workshop organized by Drug Information Association (DIA) • Co-sponsorship by AAPS, ISSX, PhRMA • Provide a focus to initiate a White Paper for completion in 2009 5

White Paper: Nature Reviews Drug Discovery 2010 Vol 9, p. 215-236 Membrane Transporters in Drug Development The International Transporter Consortium, ITC Corresponding authors: K. Giacomini, S-M. Huang and D. Tweedie  Basic Introduction and Summary of Transporter Highlights what we know   Methods for Studying Transporters Current solutions and future prospects   Drug Development Issues Decision trees  6

White Paper – What It Is and What It Is Not and what it is not….. What it is….. A consensus view on the current • A complete literature review.  thinking • A prescriptive guidance on what to What is known about the relative do and how to do it , with a clear  importance of transporters? description of what it will mean. Where should one put effort? • A consensus document that everyone  The known unknowns agrees to.  What facts are known to be untrue • A description of all of the exceptions.  (dispelling myths)? – Your experience is important and Where are our gaps in knowledge  we would certainly appreciate you (where should we increase our sharing that with the scientific knowledge)? community. A guideline (not a guidance/rules)  • Decision trees are not definitive . towards what should be considered – Included to help move the science during development. forward by acting as templates for Whitepaper biased toward NDA  discussion submission – Not must do’s 7

Transporters  Two Families of Transporters (400+ members)  30 Contribute to the efficacy and safety of drugs  ABC Transporters  ATP-binding cassette  Present in tissue barriers and excretory organs, can move compounds against a concentration gradient P-glycoprotein (P-gp, ABCB1)  Breast cancer resistance protein (BCRP, ABCG2)  Multidrug resistance proteins (MRP Family)   SLC transporters  Organic Solute Carrier Transporters  Found throughout the body, play a role in cellular homeostasis and distribution of nutrients. OATs (OAT1 - SLC22A6), OAT3 - SLC22A8)  OCT/OCTNs (OCT2 –SLC22A2)  OATPs (OATP1B1- SLCO1B1, OATP1B3-SLCO1B3)  8 2

Expression of Transporters in Major Human Organs 9 Nature Reviews Drug Discovery, 2010

Transporters Selected for Evaluation in Drug Development 10

Transporter Information in Drug Labeling P-gp Aliskiren, ambrisentan, [aprepitant], clarithromycin , colchicine, [dexvenafaxine], dronedarone , [eltrombopag], everolimus , fexofenadine, [fosaprepitant], [ixabepilone], lapatinib , maraviroc , nilotinib , paliperidone , posaconazole, [prasugrel], [[propafenone]], propranolol, ranolazine , saxagliptin, silodosin, sirolimus, sitagliptin, tipranavir** , tolvaptan , topotecan, [vorinostat] OATP1B1 Atorvastatin, cyclosporine , eltrombopag ***, lapatinib , valsartan OATP Ambrisentan OAT Sitagliptin (OAT3) OCT Metformin, pramipexole, [saxagliptin], [sitagliptin], varenicline (OCT2) BCRP Lapatinib, topotecan MRP Mycophenolate (MRP2), [ixabepilone] (MRP1),valsartan (MRP2) *Not an extensive list: data based on a preliminary survey of electronic PDR and Drugs@FDA on September 18, 2009. They are substrates, inhibitors , both substrates and inhibitors , [not a substrate or an inhibitor], or [[not studies as a substrate or an inhibitor]]; **:Tipranavir is also a P-gp inducer *** an inhibitor; its labeling contains a list of OATP1B1 substrates <Huang, SM, Zhang L, Giacomini KM, Clin Pharmacol Ther January 2010> 11

Use of Decision Trees  Pros  Evolution of concept  Generate discussion points  Offers flexibility  Cons  Rigid interpretation: prescriptive and overly cautious  Insufficient knowledge to populate the decision points  Lack of selective substrates and inhibitors  Not fully vetted “The evolution and appropriate application of the decision trees will require constant monitoring” 12

Pgp/BCRP Substrate Decision Tree Needs calibration with Positive controls Not needed in the case Not needed in the case of transfected cells of transfected cells Many drugs that are efflux substrates are extensively absorbed Factors contributing to efflux limited absorption are:   high Km, Vmax  low solubility  low permeability  metabolic stability  low dose. 13

Decision Tree for Pgp Inhibitor Interactions Needs calibration by establishing ivivc  [I 1 ] is steady-state total C max at the highest clinical dose  [I 2 ] is the GI concentration calculated at dose (mg)/250 mL 14

OATP Substrate Decision Tree Integrate preclinical and clinical data Transporter phenotyping needed 15

Relative Expression and Activity Factors Hepatocytes MDCKII-OATP1B1 cells MDCKII-OATP1B3 cells OATP1B3 OATP1B1 OATP1B3 OATP1B1 E-sul CCK-8 CCK-8 E-sul Relative Expression Factor (REF) Relative Activity Factor (RAF) CL Exp  Hep, ESul  Hep, OATP1B1 RAF REF OATP1B1 OATP1B1 CL Exp OATP1B1, ESul OATP1B1, OATP1B1 CL Exp  Hep, CCK8  Hep, OATP1B3 RAF REF OATP1B3 OATP1B3 CL Exp OATP1B3, CCK8 OATP1B3, OATP1B3 16 Shitara et al., 2006

REF for OATP1B1 and OATP1B3 OATP1B1 OATP1B3 MDCK MDCK/OATP1B3 Human Hepatocytes MDCK MDCK/OATP1B1 Human Hepatocytes 30ug 10ug 20ug 30ug 10ug 20ug 30ug 30ug 10ug 20ug 30ug 10ug 20ug 30ug OATP1B3 OATP1B1 3.5 1.6 band density(relative value) MDCKII/OATP1B1 band density(relative value) MDCKII/OATP1B3 3 1.4 Human Hepatocytes Human Hepatocytes 2.5 1.2 1 2 0.8 1.5 0.6 1 0.4 0.5 0.2 0 0 0 10 20 30 40 0 10 20 30 40 protein amount (ug/lane) protein amount (ug/lane) REF OATP1B1 = Exp Hep,OATP1B1 / Exp OATP1B1, OATP1B1 = 16.9 REF OATP1B3 = Exp Hep,OATP1B3 / Exp OATP1B3, OATP1B3 = 2.8 17

RAF for OATP1B1 and OATP1B3 RAF OATP1B1 = CL Hep,E-sul / CL OATP1B1, E-sul = 16.2 E-sul uptake into MDCKII-OATP1B1 cells E-sul uptake into human hepatocytes 7.0 E-sul initial uptake rate 1000 OATP1B1-mediated E-sul (pmol/10^6cells/min) 6.0 (pmole/10^6 cells/min) Total Uptake 800 5.0 Passive diffusion uptake rate Active Uptake 4.0 600 Observed data V max / K m = 18.3 3.0 V max / K m = 295.6 400 (µl / 10 6 cells/min) 2.0 (µl /10 6 cells/min) 200 1.0 0 0.0 0 5 10 15 20 25 30 0 2 4 6 8 10 12 [E-sul] uM [E-sul] uM RAF OATP1B3 = CL Hep,CCK-8 / CL OATP1B3, CCK-8 = 3.4 70 CCK-8 uptake into MDCKII-OATP1B3 cells CCK-8 uptake into human hepatocytes CCK-8 initial uptake rate (pmole/10^6cells/min) 60 35.0 OATP1B3-mediated CCK-8 Total Uptake (pmole/10^6 cells/min) 50 30.0 Passive diffusion 25.0 40 uptake rate Active Uptake 20.0 Observed data 30 V max / K m = 13.0 15.0 20 V max / K m = 3.9 (µl / 10 6 cells/min) 10.0 10 (µl /10 6 cells/min) 5.0 0 0.0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 18 [CCK-8] uM [CCK-8] uM

Relative Contribution of OATPs to Pitavastatin Uptake Clearance Transporter Km Vmax CL int (uM) (pmole/min/10^6cells) (ul/min/10^6cells) OATP1B1 4.5±1.2 18.8±1.3 4.2 OATP1B3 6.5±3.2 9.3±1.7 1.4 Transporter Cl int RAF Estimated Relative REF Estimated Relative CL int from contribution CL int from contribution (ul/min/10^6c ells) RAF REF (%) (%) OATP1B1 4.2 16.2 67.5 93.4 16.9 70.8 94.7 OATP1B3 1.4 3.4 4.8 6.6 2.8 4.0 5.3 OATP1B1 is the major transporter for the hepatic uptake of pitavastatin  in human hepatocytes Data obtained by RAF and REF methods are comparable  19

OATP Inhibition Decision Tree Could this result in false negatives for liver targeted compounds? Most sensitive probe needs to be established 20